BEIJING (AP) — Parts of a northern Chinese city have been quarantined after state media said a man there died of bubonic plague.

China’s official Xinhua News Agency said Tuesday that 151 people were under observation in the city of Yumen in Gansu province after authorities determined they had come in contact with a man who died of the plague July 16.

Investigators believe the man contracted the bacterial infection after contact with a marmot, Xinhua said.

The report said all the people under quarantine were in good health, but that 10 checkpoints were still blocking off parts of the city of about 180,000.

Bubonic plague killed millions of people in Europe in the 14th century and tens of thousands in China in the 19th century. It remains endemic in northwest China and is spread largely through flea bites. The bacteria can cause gangrene, seizures and fever.